The overall objective is to know the molecular, toxicological and pharmacological properties of the ionic channel associated with the nicotinic acetylcholice (ACh) receptor and to understand the mechanism by which this receptor and its channel activate and control ionic permeability across the postsynaptic membrane. The receptor and its ionic channel have totally different drug and toxin specificities, and recent data suggest that they may be two proteins rather than subunits of a single molecule. Torpedo electric organ is used as a tissue source rich in these proteins. The ionic channel is identified in vitro by its specific binding of (3H)perhydrohistrionicotoxin, which is determined by equilibrium dialysis and centrifugal assay. Toxins (e.g., histrionicotoxin analogs) and drugs (e.g., quinacrine and peperocaine) which inhibit this binding may be found to interact with this channel as a primary or secondary target. Also, whether or not nereisotoxin and cartap interact with the ionic channel will be established. Derivatives of the anti-parkinson and antiviral drug, amantadine, will be tested so as to determine if there is correlation between their antiviral potency and their inhibition of the ionic channel. The channel will be purified and its chemical nature, molecular weight and subunits studied. Rat brain will be used to search for a similar ionic channel in central neurones. The purified ionic channel, alone and with the purified ACh-receptor, will be reconstituted into synthetic liposomes and 22Na flux studied in presence and absence of specific drugs and toxins. Whether or not the ionic channel is phosphorylated or dephosphorylated will be established by incubation of the membranes with (32P)alpha-ATP, followed by purification of the ionic channel. Antibodies against the ionic channels will be obtained from immunized rabbits and utilized to study its structure. If these rabbits develop muscular paralysis, they may represent another animal model for myasthenia gravis.